1. Field of the Invention
This invention relates to a method for preventing damage to an integrated circuit from occurring, and more particularly to a method for preventing damage to a gate oxide layer from a well in a complementary metal-oxide semiconductor (CMOS) device, during a plasma fabrication process.
2. Description of Related Art
In the current process for fabricating an integrated circuit (IC) device, each fabrication process may cause an accumulation of static charges in the integrated circuit device. When the accumulated static charges exceed a certain level, the IC device may be damaged without being noticed. This can also cause, for example, an electrical property shift, a decrease in production rate, or a deterioration of reliability.
The static charges usually accumulate at a bonding pad region. As the accumulated static charges exceed a tolerance, the static charges may break the gate oxide layer and cause damage to it. The reason why the static charges accumulate on the bonding pad region is that the bonding pad region is a good conductor with a large area behaving like a large antenna, which can easily accumulate static charges. It is more obvious for a plasma process, which is widely used for purposes of, for example, etching, removing photoresist, or depositing insulating layer. The accumulated static charges drift to a transistor gate through interconnect metal lines. Since the gate is usually enclosed by an insulating layer, the accumulated static charges cannot drift away and result in damaging the gate oxide layer. The reliability and properties of the device are therefore affected. As the accumulated static charges exceed a certain level, the gate oxide layer may breakdown and the device is further damaged. This phenomenon is called an antenna effect.
In a CMOS device, there is an N(P)-type well on a P(N)-type substrate. During a plasma-related process, the substrate is grounded so that there is no bias on the CMOS device but the N(P) well is in a floating state. The floating well very easily accumulates static charges, which may break the gate oxide layer.